Biceps femoris accessory tendon tenodesis: A case report

Key Clinical Message We present a case of lateral knee pain from snapping of an accessory tendinous insertion of the biceps femoris. After failure of conservative treatment options, tenodesis of the accessory band to the direct arm insertion at the posterolateral edge of the fibular head effectively resolved symptoms. Abstract There are several distinct causes of lateral knee pain including IT band syndrome, meniscus tears, or other soft tissue pathologies; however, a few case reports have shown the biceps femoris as a cause of lateral knee pain and snapping. Conservative treatment is of modest benefit to the patient in these scenarios, and an MRI is not always able to identify the accessory band, as in our case. Intraoperatively, we discovered an accessory band of the biceps femoris attaching to the anterolateral tibia, causing pain and snapping during knee flexion as the band passed over the fibular head. There have been various surgical attempts to address this pathology; however, we report a successful outcome after tenodesis of the accessory band to the direct insertion at the posterolateral fibular head.


| INTRODUCTION
2][3][4] In rare instances, snapping lateral knee pain may also be caused by the distal tendon of the biceps femoris long head shifting over the fibular head. 5,6egardless, the various differential diagnoses should be properly ruled out by a careful history, a detailed physical exam, and advanced imaging.
Few cases of snapping biceps femoris tendons have been recorded in the literature across various case reports.Causes of the snapping biceps femoris tendon have been attributed to anomalous insertions (most prevalent), [7][8][9][10][11][12][13][14][15][16] tendon subluxation, 17,18 abnormalities of the fibular head, [19][20][21][22][23] or secondary to trauma. 6,24Conservative treatment is usually attempted first and consists of physical therapy and anti-inflammatory medications.Surgery, which is usually the last resort and the most effective, consists of resecting the anomalous tendon insertion or correcting any fibular deformities. 7,19n this report, we present a patient with lateral knee pain from an accessory insertion of the snapping biceps femoris tendon and discuss surgical exploration and repair.The patient was informed that his case would be submitted for publication and he provided consent.

| CASE REPORT
A 48 year-old male patient presented to our clinic with lateral right knee snapping and pain that had been ongoing for over 2 years without trauma or other known cause.The patient noted the pain and snapping at the fibular head worsened with cycling and deep squats.On examination, no atrophy was noted; however, snapping was visible at knee flexion past 90 degrees.The patient had attempted activity modification, a home-exercise program and icing without relief.Radiographs of the knee were unremarkable with no evidence of any osseous abnormalities or bony prominences at the fibular head.MRI imaging of the right knee did not indicate evidence of an anatomical variant or anomalous insertion of the biceps femoris tendon (Figure 1).After 8 weeks of physical therapy focused on knee conditioning and hamstring strengthening, the patient reported worsening of symptoms and elected to proceed with surgery as conservative options had been exhausted.

| OPERATIVE FINDINGS AND TECHNIQUE
The patient was positioned supine on the operating table with a bump under the thigh.Preoperative antibiotics and general anesthesia with a peripheral nerve block were administered.After all bony landmarks were identified, a 4-cm curvilinear incision was made over the proximal fibula (Figure 1).Careful dissection was taken down to the level of the biceps femoris tendon using Metzenbaum scissors and electrocautery.The self-retaining retractors were used to better visualize the insertion of the tendon.Care was taken to protect the common peroneal nerve and other neurovascular structures.The tendon was inspected and a thick band was visualized inserting on the anterolateral tibia (Figure 2).The knee was then flexed to recreate the snapping and it was apparent that this band was the source of the snapping (Video S1).Upon further inspection, the direct band of the biceps femoris tendon was revealed.At this point, it was decided to dissect the anomalous insertion from the tibia (Figure 3) and repair this tendon down to the direct biceps femoris insertion on the posterior head of the fibula.A No. 2 Ethibond suture was used to secure the released tendon down on the direct band of the tendon (Figure 4).The released anomalous insertion of biceps femoris tendon was successfully repaired down to the direct band of the tendon (Figure 5).The knee was tested with flexion to ensure that there were no structures snapping at this time (Video S1).
F I G U R E 1 MRI of the right knee indicating no evidence of tear or peritendinous edema adjacent to the distal biceps femoris tendon or evidence of variant anatomy.
At his first postoperative appointment, snapping at the lateral knee was visually confirmed to have been resolved.The patient was non-weight bearing on the operative leg for one month after surgery and was counseled to regularly perform passive range of motion exercises to prevent stiffness.After 1 month, he transitioned to being full weight bearing and began physical therapy to regain full range of motion.At his 2-month follow-up, the patient's pain had completely resolved and he had full range of motion.He was able to resume his normal activities.

| DISCUSSION
The anatomy of the biceps femoris tendon is complex and crucial to the biomechanical function of the knee.The muscle, composed of the short and long heads, is involved with hip extension, lateral rotation of the leg, and knee flexion. 25In addition, the biceps femoris plays an important role as a dynamic stabilizer of the knee and injury has been associated with rotatory instability of the knee. 25  to the lateral condyle of the femur, popliteus, and the arcuate popliteal ligament. 26The long head of the biceps femoris originates at the ischial tuberosity and has two tendinous insertions.The first is a direct arm that attaches to the posterolateral fibular head and the second is an anterior arm that attaches to the lateral aspect of the fibular head or the lateral tibial plateau. 16,26In our case, an anomalous attachment of the biceps femoris to the anterolateral tibia was repositioned to the direct arm insertion to resolve painful snapping of the tendon over the fibular head.
Due to the unremarkable findings on imaging, the diagnosis of a snapping knee due to an accessory tendon is difficult.There is some evidence to suggest that use of dynamic ultrasound may aid in making the diagnosis of a snapping biceps femoris tendon. 27However the diagnosis is often made clinically, as in our case, with positive findings presenting during the physical examination. 5,10arious surgical approaches have been used to treat snapping of the biceps femoris tendon.One such approach is resection of the fibular head. 19,20McNulty et al. successfully resolved symptoms by removing the prominent ridge on the posterior aspect of the fibular head, which caused snapping. 19Fung et al. reported a 17-year-old soccer player with bilateral exostoses at the fibular head treated surgically with exostosis excision, biceps tendon debridement, and fibular prominence smoothening with success. 20n other case reports, the anomalous tendon insertions may be resected. 5,13,16Fritsch et al., 5 reported an enlarged anterior arm of the biceps femoris tendon which elicited snapping.The thickened anterior arm was then detached and shuttled through a fibular tunnel, which resolved the snapping.Further, Reid et al. 16 reported painful snapping in a 15-year-old athlete, which was resolved through resection of the accessory biceps femoris attachment and reinsertion into the fibular head with suture anchors and a Krackow suture.In Ernat et al., 13 the anterolateral tibial and thickened fibular accessory bands were released without reattachment, which resolved snapping at the lateral knee.
In Date et al., 10 an anomalous insertion of the biceps femoris at the anterolateral proximal tibia as well as the anterior arm at the lateral edge of the fibular head were sutured to the direct arm on the posterolateral fibular head using three stitches.Similar to Date's case, the accessory band of our patient's biceps femoris tendon was sutured against the direct arm and periosteum with only stitches without the use of suture anchors.In addition, given the crucial role of the biceps femoris to knee function, we felt that reattachment of the accessory biceps femoris tendon insertion was more appropriate than a tenotomy alone.
In our patient, conservative management with antiinflammatory medications and 2 months of physical therapy was initially attempted; however, these interventions failed to relieve his pain or snapping.Further, radiographs did not identify any abnormal features at or prominence of the fibular head that would have indicated a fibular head resection.Given the patient's visible, symptomatic lateral knee snapping and lack of relief from conservative treatment, the patient opted for surgical biceps femoris insertion exploration with possible accessory band release and transposition.Following surgery, our patient experienced successful resolution of symptoms and was able to return to an active lifestyle at 2 months follow-up without recurrence of symptoms.Our unique case contributes to the existing literature by demonstrating an accessory anterolateral tibial insertion of the biceps femoris tendon as the underlying cause of painful snapping over the fibular head.Past cases of snapping biceps femoris tendons at the lateral knee have been treated uniquely depending on their pathophysiological root.When conservative treatments prove ineffective, surgical intervention emerges as a viable solution.In our case, symptoms were successfully resolved by the tenodesis of the accessory band to the direct arm insertion at the posterolateral edge of the fibular head.

| CONCLUSION
Snapping of the biceps femoris tendon is a relatively rare occurrence that can cause painful and audible clicking that interferes with a patient's lifestyle.Conservative treatment is usually unable to resolve symptoms.There have been a variety of surgical approaches aimed at treating this anomaly.Accessory tendon tenodesis to the posterior head of the fibula may preserve knee stability and allow for quick recovery times and resolution of symptoms.We present a rare case of an anomalous insertion of the biceps femoris tendon that was resected and reattached surgically to resolve pain and snapping.Ultimately, further research is needed to evaluate the long-term success of such surgeries and their effects on knee mobility.

AUTHOR CONTRIBUTIONS
A cadaveric study of 56 knees by Salter et al. 2005 found that the biceps femoris tendon is composed of medial and lateral slips and was found to attach F I G U R E 2 Intraoperative view of the lateral right knee flexed to 90 degrees with the patient positioned supine.The 4-cm curvilinear incision is positioned squarely over the proximal fibula (arrow).

F I G U R E 3
Flexed lateral knee.A thick band (arrow) can be visualized inserting on the anterolateral tibia.F I G U R E 4 Right knee in full extension.The anomalous tendon insertion (arrow) has been resected and the thickness can be compared with that of the tendon's direct band (star).F I G U R E 5 Right knee in full extension.The released anomalous insertion of biceps femoris tendon has been repaired down to the direct band of the tendon (arrow).